Whole beam image splitting system

ABSTRACT

The present invention comprises methods and apparatuses for causing a single imaging lens system to simultaneously form multiple high resolution images on multiple imaging sensor planes. The images are preferably substantially identical, with no parallax error, except for different light levels so that the multiple images are of sufficient quality and similarity that they may be compared and/or combined (typically pixel-by-pixel) to create a single instantaneous high dynamic range (HDR) image. The invention may be used to create high-resolution HDR snapshots of moving subjects, as well as high-resolution HDR moving pictures (e.g. cinematographic films, movies, or other video) in which the subject and/or camera is moving. Alternatively, the images are substantially identical except for different focuses.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/414,547, entitled “Whole Beam Image Splitting System”, filed on Mar.30, 2009 and issued as U.S. Pat. No. 8,320,047 on Nov. 27, 2012, whichclaims priority to and the benefit of filing of U.S. Provisional PatentApplication Ser. No. 61/040,300, entitled “Method and Apparatus forProducing Multiple High-Resolution Images Using a Single Imaging LensSystem”, filed on Mar. 28, 2008; U.S. Provisional Patent ApplicationSer. No. 61/107,951, entitled “Method and Apparatus for ProducingMultiple High-Resolution Images Using a Single Imaging Lens System”,filed on Oct. 23, 2008; and U.S. Provisional Patent Application Ser. No.61/116,078, entitled “Method and Apparatus for Producing MultipleHigh-Resolution Images Using a Single Imaging Lens System”, filed onNov. 19, 2008, all of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention (Technical Field)

The present invention relates generally to the field of multiple imagingsystems, more specifically to methods and apparatuses for causing asingle imaging lens system to simultaneously form multiple images onmultiple imaging sensor planes. The images are preferably substantiallyidentical except for different light levels so that the multiple imagesare of sufficient quality and similarity that they may be comparedand/or combined (typically pixel-by-pixel) to create a singleinstantaneous high dynamic range (HDR) image. Alternatively, the imagesare substantially identical except for different focuses or differentmagnifications.

2. Description of Related Art

Note that the following discussion refers to a number of publicationsand references. Discussion of such publications herein is given for morecomplete background of the scientific principles and is not to beconstrued as an admission that such publications are prior art forpatentability determination purposes.

In recent years, the goal of producing high dynamic range (HDR) imageshas been approached from many different directions. U.S. Pat. Nos.7,084,905 and 7,397,509 and U.S. Pat. Appl. Ser. Nos. 2005/0099504 and2008/0112651 each describe an apparatus and/or method for producing HDRimages using specialized sensor arrays with novel pixel properties. U.S.Appl. No. 2008/0055683 describes a system and method for synthesizing anHDR image using a single optical image. U.S. Pat. No. 5,801,773 and U.S.Pat. Appl. Ser. Nos. 2005/0041113, 2006/0209204, 2007/0025717, and2008/0094486 each describe an apparatus and/or method for synthesizingHDR images from sequences of images taken at different moments in time.None of these patents describe a method for optically producing multipleimages on multiple sensor arrays simultaneously.

Devices and methods for optically producing multiple simultaneous imageshave been known for over 100 years. U.S. Pat. No. 347,451 describes anapparatus for using multiple imaging lenses to create simultaneousimages on a single image plane. U.S. Pat. Nos. 3,601,480, 5,153,621,5,194,959, 5,734,507, 5,835,278, and 5,926,283, European Pat. Appl. No.91118422.4 (Publication number 0 484 802 A2), Japanese PatentPublication No. 60-213178, and Aggarwal & Ahuja, Split Aperture Imagingfor High Dynamic Range, International Journal of Computer Vision 58(1),7-17 (2004) each describe a method and/or apparatus for splitting animage-forming beam into spatially-distinct sections using apyramid-shaped mirror or other total reflective device. U.S. Pat. Nos.5,024,530, 5,642,191, 6,856,466, and 7,177,085 each describe a methodand/or apparatus for splitting an image-forming beam intospatially-distinct sections using a prism or other refractive device.All of these papers and patents describe methods and/or apparatuses thatsuffer from parallax error, due to the fact that the image-forming beamin each case is split into subsections that are spatially distinct fromone another at the point of splitting. None of these patents or papersdescribe or suggest a method for splitting an image-forming beam using apartially-reflecting beamsplitting device that provides light for eachsplit portion from the entire original image-forming beam.

The use of prisms and/or beamsplitters to form a plurality of subimageshaving different color or polarization characteristics has been studiedand explained in great depth. U.S. Pat. Nos. 2,560,351, 2,642,487,2,971,051, 3,202,039, 3,381,084, 3,653,748, 3,659,918, 3,668,304,3,802,763, 3,945,034, 4,009,941, 4,268,119, 4,933,751, 5,134,468, and7,283,307 each describe a method and/or apparatus that explicitly splitsthe image-forming beam into separate subimages on the basis of color(using explicitly dichroic and/or color-separating means). None of thesepatents describe a method for splitting an image-forming beam intosubimages that have identical color and/or wavelength properties.Furthermore, U.S. Pat. Nos. 3,202,039, 3,659,918, 3,802,763, 4,009,941,4,084,180, 4,268,119, 5,134,468, and 6,215,597 each describe a methodand/or apparatus that relies on passing the image-forming beam throughsolid glass prisms that have tilted glass faces in contact with air: asituation that immediately precludes their use for producing multiplehigh-resolution sub-images with identical color and/or wavelengthproperties.

SUMMARY OF THE INVENTION

The present invention is a method of creating multiple images, themethod comprising the steps of splitting an image-forming optical beaminto a plurality of beam portions using a plurality of whole beam broadspectrum beamsplitters forming a plurality of images on separate opticaldetectors from at least some of the plurality of the beam portions. Thesplitting step optionally comprises splitting the image-forming beaminto a first reflected beam portion and a first transmitted beam portionusing a first whole beam broad spectrum beamsplitter, and splitting thefirst reflected beam portion into a second reflected beam portion and asecond transmitted beam portion using a second whole beam broad spectrumbeamsplitter. In this case, the method optionally further comprises thestep of transmitting the second reflected beam portion through the firstbeamsplitter to form a third transmitted beam portion, wherein theforming step comprises forming multiple images using the first, second,and third transmitted beam portions. Alternatively in this case theforming step comprises forming multiple images using the firsttransmitted beam portion, the second transmitted beam portion, and thesecond reflected beam portion. The splitting step alternativelycomprises splitting the image-forming beam into a first reflected beamportion and a first transmitted beam portion using a first whole beambroad spectrum beamsplitter, and splitting the first transmitted beamportion into a second reflected beam portion and a second transmittedbeam portion using a second whole beam broad spectrum beamsplitter. Inthis case, the forming step optionally comprises forming multiple imagesusing the first reflected beam portion, the second reflected beamportion, and the second transmitted beam portion. Alternatively in thiscase, the method further comprises the step of reflecting the secondreflected beam portion from the first beamsplitter to form a thirdreflected beam portion, wherein the forming step preferably comprisesforming multiple images using the first reflected beam portion, thesecond transmitted beam portion, and the third reflected beam portion.

The method optionally comprises the step of correcting aberrations inthe beam portions which have been transmitted through at least onebeamsplitter using an element selected from the group consisting of acurved back surface of the first beamsplitter, a curved front surface ofthe second beamsplitter; a curved back surface of the secondbeamsplitter, the first beamsplitter comprising a doublet lens, thesecond beamsplitter comprising a doublet lens, and at least onecorrective lens system.

The first beamsplitter is optionally constructed by coating a surface ofa first prism and/or a first surface of a second prism with a firstpartially-reflecting coating and bonding the first and second prismstogether so the first coating is disposed between the first prism andthe second prism, the coating thereby forming the first beamsplitter;and wherein the second beamsplitter is constructed by coating a surfaceof a third prism and/or a second surface of the second prism with asecond partially-reflecting coating and bonding the second and thirdprisms together so the second coating is disposed between the secondprism and the third prism, the coating thereby forming a secondbeamsplitter. In this case, the method preferably further comprises thestep of pre-correcting aberrations induced in the beam portions by theprisms using a corrective lens system disposed prior to the firstbeamsplitter.

The forming step preferably comprises simultaneously capturing an imageon each optical detector. The simultaneously captured images arepreferably substantially identical except for their light levels. Thismethod preferably further comprises the step of selecting reflectanceand transmittance values of the beamsplitters in order to achievedesired light levels of the images. This method preferably furthercomprises the step of combining at least two of the simultaneouslycaptured images to form a high dynamic range image, and preferablyfurther comprises the step of assembling a plurality of the high dynamicrange images to create a high dynamic range film or video. Thesimultaneously captured images are optionally substantially identicalexcept for their focuses, in which case the method preferably furthercomprises the steps of selecting one image from each set ofsimultaneously captured images and assembling the selected images tocreate a film or video, wherein the selecting step preferably comprisesfirst selecting an image formed on a first optical detector and thenselecting an image formed on a second optical detector in order tochange a focus of a scene in the film or video. The simultaneouslycaptured images are optionally substantially identical or substantiallyidentical except for their magnifications.

The method optionally comprises the step of causing only one of theoptical detectors to capture an image at a time, thereby increasing acamera framerate. The method optionally further comprises the step ofeffectively collimating the image forming optical beam, in which casethe method preferably further comprises the step of focusing each of thebeam portions which is intended to form an image onto a correspondingoptical detector prior to the forming step.

The present invention is also an apparatus for creating multiple images,the apparatus comprising a plurality of whole beam broad spectrumbeamsplitters for splitting an image-forming optical beam into aplurality of beam portions; and a plurality of separate opticaldetectors for imaging at least some of the plurality of beam portions.The apparatus preferably further comprises an image forming lens forforming the image-forming optical beam. The apparatus preferablycomprises a first whole beam broad spectrum beamsplitter oriented at aforty-five degree angle to an optical axis of the image forming beam,the first beamsplitter forming a first reflected beam portion and afirst transmitted beam portion. The apparatus optionally comprises asecond whole beam broad spectrum beamsplitter oriented at a forty-fivedegree angle to the first beamsplitter and perpendicularly to an opticalaxis of the first reflected beam portion or the first transmitted beamportion. The second beamsplitter is optionally oriented at a ninetydegree angle to the first beamsplitter and at a forty-five degree angleto an optical axis of the first reflected beam portion or the firsttransmitted beam portion. The second beamsplitter is optionally orientedparallel to the first beamsplitter and at a forty-five degree angle toan optical axis of the first reflected beam portion or the firsttransmitted beam portion.

At least one of the beamsplitters is optionally selected from the groupconsisting of a thin beamsplitter, a glass plate, a pellicle, a doubletlens, and an achromatic cemented doublet. At least one of thebeamsplitters optionally comprises a curved back surface and/or a curvedfront surface. The apparatus optionally further comprises at least onecorrective lens system disposed between one of the beamsplitters and oneof the optical detectors. The beamsplitters optionally comprise adeposited partially-reflective layer disposed between two prisms, inwhich case the prisms are preferably bonded together, and at least oneof the prisms preferably comprises two faces, each face bonded to aseparate prism. In this case the apparatus preferably further comprisesa corrective lens system disposed between the image forming lens and afirst the beamsplitter.

The plurality of optical detectors are preferably configured tosimultaneously capture an image on each optical detector. In this casethe beamsplitters preferably comprise reflectance and transmittanceselected to achieve desired light levels of the images on each opticaldetector. The simultaneously captured images are preferablysubstantially identical except for their light levels. At least two ofthe simultaneously captured images are preferably combined to form ahigh dynamic range image. A plurality of the high dynamic range imagesare preferably assembled to create a high dynamic range film or video.The simultaneously captured images are optionally substantiallyidentical, substantially identical except for their focuses, orsubstantially identical except for their magnifications. The opticaldetectors are optionally configured so that only one of the opticaldetectors captures an image at a time, thereby increasing a cameraframerate.

The apparatus preferably further comprises a collimating lens system foreffectively collimating the image forming optical beam, in which case afield lens is optionally located substantially coincident with anintermediate image plane of the image forming optical beam. In thiscase, the apparatus preferably further comprises at least one imaginglens system for focusing each beam portion which is intended to form animage onto a corresponding optical detector.

Objects, advantages and novel features, and further scope ofapplicability of the present invention will be set forth in part in thedetailed description to follow, taken in conjunction with theaccompanying drawings, and in part will become apparent to those skilledin the art upon examination of the following, or may be learned bypractice of the invention. The objects and advantages of the inventionmay be realized and attained by means of the instrumentalities andcombinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated into and form a partof the specification, illustrate several embodiments of the presentinvention and, together with the description, serve to explain theprinciples of the invention. The drawings are only for the purpose ofillustrating a preferred embodiment of the invention and are not to beconstrued as limiting the invention. In the drawings:

FIG. 1A is a schematic of an embodiment of the present inventioncomprising two beamsplitters.

FIG. 1B is a schematic of an embodiment of the present inventioncomprising two beamsplitters.

FIG. 2 is a schematic of the embodiment shown in FIG. 1A comprisingadditional corrective lenses.

FIG. 3 is a schematic of the embodiment shown in FIG. 1A wherein one ofthe beamsplitters is shaped to correct aberrations.

FIG. 4 is a schematic of the embodiment shown in FIG. 1A wherein one ofthe beamsplitters comprises a doublet beamsplitter.

FIG. 5A is a schematic of another embodiment of the present inventioncomprising two beamsplitters.

FIG. 5B is a schematic of another embodiment of the present inventioncomprising two beamsplitters.

FIG. 6 is a schematic of the embodiment shown in FIG. 5A comprisingadditional corrective lenses.

FIG. 7 is a schematic of the embodiment shown in FIG. 5A but comprisingshaped beamsplitters.

FIG. 8 is a schematic of an embodiment of the present inventioncomprising solid prisms and two beamsplitting elements.

FIG. 9 is a detail of the corrective lens system utilized in theembodiment shown in FIG. 8.

FIGS. 10A-C are details of the prisms utilized in the embodiment shownin FIG. 8.

FIGS. 11A-C are side, top, and end views respectively of an embodimentof the present invention comprising prisms comprising four beamsplittingelements which can form five substantially identical images.

FIG. 12 is a tilted see-through view of the embodiment of FIGS. 11A-C.

FIG. 13 is a schematic of another embodiment of the present inventioncomprising solid prisms and two beamsplitting elements.

FIG. 14 is a detail of the corrective lens system utilized in theembodiment shown in FIG. 13.

FIGS. 15A-C are details of the prisms utilized in the embodiment shownin FIG. 13.

FIG. 16 is an embodiment of the present invention comprising acollimating lens.

FIG. 17 is another embodiment of the present invention comprising acollimating lens.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the system of this invention are described herein below.Although the embodiments are described with specificity, and are shownhaving specific component parameters, it should be noted that the systemof this invention is not limited to those parameter ranges. In theembodiments described herein, although the characteristics of theelements are stated with specificity, it should be noted that thespecific value of any of the characteristics of any element of theembodiment is provided to within engineering tolerances. Engineeringtolerances as utilized herein include the tolerances within whichelements can be procured and the tolerances within which the designperforms the desired function.

As used herein “a” means one or more unless otherwise indicated.

As used throughout the specification and claims, the term “beamsplitter”means a partially reflecting optical element that can both transmit andreflect incident light, including but not limited to a partiallyreflecting mirror, a pellicle, or an optical coating or layer.

As used throughout the specification and claims, the term “whole beam”means utilizing light from the entire spatial cross-sectional area (e.g.width and height) of an optical beam in each of the inputs and outputs.For example, a “whole beam” beamsplitter is one that splits the entirecross-section of an input beam into two or more output beams, each ofwhich utilizes light from the entire cross-sectional area of the inputbeam.

As used throughout the specification and claims, the term “beam portion”means an optical beam which has been reflected from, or transmittedthrough, a beamsplitter, for example a whole beam broad spectrumbeamsplitter.

As used throughout the specification and claims, the term “light level”means the radiant power of a light beam used to form an entire image.

As used throughout the specification and claims, the term “opticaldetector” means a detector, image sensor, CMOS sensor, CCD sensor,linear detector array, film, celluloid, or any other optically sensitivemedium or device.

As used throughout the specification and claims, the term “broadspectrum beamsplitter” means a beamsplitter whose transmittance issufficiently constant with respect to wavelength across a desiredwavelength range, and whose reflectance is sufficiently constant withrespect to wavelength across the desired wavelength range, so as toensure substantially identical images are produced by its reflected andtransmitted beam portions.

As used throughout the specification and claims, the term “effectivelycollimated” in reference to an image beam means that the image beam hasa maximum divergence or convergence half-angle of less thanapproximately 20 degrees. That is, the maximum angle between the opticalaxis and the propagation direction of any ray within an effectivelycollimated image beam is less than approximately 20 degrees.

As used throughout the specification and claims, the term “substantiallyidentical” means that any differences in optical properties, includingbut not limited to line-of-sight direction, wavelength composition,spatial image composition, spatial structure, geometric aberrations,diffraction aberrations, chromatic aberrations, geometric imagedistortion, light level, focus, and magnification, are at leastsufficiently small so as not to be generally discernable by a standardhuman observer. For example, two images are considered “substantiallyidentical” if the sum of all differences between the images is smallerthan the size of the greater of (a) the pixel size of the system sensor;or (b) the diffraction Airy disc size for the system. For the purposesof the present invention, substantially identical images may bereflected about an axis and/or rotated with respect to one another andstill be considered substantially identical. Thus two images areconsidered “substantially identical” if they appear to a standard humanobserver to be generally identical except, for example, that one imageis a mirror image of the other.

As used throughout the specification and claims, the term “intermediateimage plane” means a virtual plane in space where light has been causedby preceding optical elements to form a real image.

As used throughout the specification and claims, when referring to abeamsplitter, the term “thin” means that a beamsplitter is sufficientlythin so that any optical aberrations the beamsplitter adds to the systemare lesser in extent or smaller than the aberrations inherent in thesystem when the beamsplitter is not present. That is, any suchaberrations are sufficiently minimized so that they system can formsubstantially identical images,

FIG. 1A is a schematic diagram of embodiment 100 of the presentinvention which utilizes a pair of beamsplitters to split the light froma single imaging system so as to produce three spatially-identicalimages on three separate detector planes. Referring to FIG. 1A, opticalradiation 110 preferably from an object (not shown) is incident onimaging lens system 112. Any imaging or image forming lens system may beused in this embodiment of the invention. For example, any of the cameralenses manufactured by Nikon, Olympus, Panavision, or Thales Angenieuxmay be used as imaging lens system 112. Image-forming beam 114 exits theimaging lens system 112 as a converging image beam and is incident onbeamsplitter 118, preferably oriented at a 45-degree angle to the pathof image-forming beam 114.

Beamsplitter 118 is preferably thin; for example it may be 0.5 mm thickand made of glass with flat and parallel front and back surfaces; or itmay comprise a so-called “pellicle” beamsplitter, such as Part NumberNT39-482 from Edmund Optics. In practice, it has been found that, inorder to minimize aberrations sufficiently to form substantiallyidentical images, beamsplitter 118 should preferably be thin, sincegeometric aberrations caused by the tilted glass/air interfaces ofbeamsplitter 118 increase in size as the thickness of beamsplitter 118increases. In some embodiments, as a general measure, the beamsplitterthickness is preferably less than approximately 100 times the greater ofeither of these two values: (a) the pixel width of an individual pixelin an image sensor; or (b) the diffraction spot size, or Airy discdiameter, of the imaging lens system or front lens of the system.

As a result of this beamsplitter arrangement, first transmitted beamportion 120 continues toward image sensor 116, where it forms an image,and first reflected beam portion 122 is reflected toward and is incidenton beamsplitter 124, which is preferably oriented perpendicular to firstreflected beam portion 122. As a result, second transmitted beam portion126 forms an image on image sensor 128, while second reflected beamportion 130 returns toward beamsplitter 118, which transmits thirdtransmitted beam portion 132 which forms an image on image sensor 134.

In order to avoid vignetting (obscuration of a portion of light reachinga detector) of image-forming beam 114, the distance D1 between the backof imaging lens system 112 and the center of beamsplitter 118, distanceD2 between the center of beamsplitter 118 and the center of beamsplitter124, and the distance D3 between the center of beamsplitter 118 and thecenter of image sensor 134 are each preferably greater than or equal toone-half of the diameter of image forming beam 114. Unless variations infocus are desired (as discussed below), the total optical path lengthtraveled by the image forming beam 114 is preferably the same whenmeasured over its total path to each of sensors 116, 128, and 134. Inthat case the distance between the center of beamsplitter 118 and thecenter of image sensor 116 is equal to [D3+(2*D2)], and the distancebetween the center of beamsplitter 124 and the center of image sensor128 is equal to [D2+D3]. Furthermore, the back focal distance, which isthe distance between the back of the imaging lens system 112 and itsnatural focal plane, is preferably approximately equal to[D1+(2*D2)+D3]. In this case, the images formed on each of the imagesensors are substantially identical, preferably except for differentlight levels, as described next.

The portion of the radiant power of the original image forming beam 114that is present in the image formed on image sensor 116 is equal to(1−R1−A1), where R1 is the reflectance and A1 is the absorbance ofbeamsplitter 118. The value of R1 may be chosen to be anything in therange between 0 and 1.0. The portion of the radiant power of theoriginal image forming beam 114 that is present in the image formed onimage sensor 128 is equal to [R1*(1−R2−A2)], where R2 is the reflectanceand A2 is the absorbance of beamsplitter 124. The value of R2 may bechosen to be anything in the range between 0 and 1.0. The portion of theradiant power of the original image forming beam 114 that is present inthe image formed on image sensor 134 is equal to [R1*R2*(1−R1−A1)]. Withthese three equations, any set of light level ratios between the sensor116, sensor 128, and sensor 134 may be achieved by selecting the propervalues for R1 and R2.

For example, if it is desired to achieve a light level ratio betweensensor 116 and sensor 128 of 2:1, and a light level ratio between sensor116 and sensor 134 of 4:1, and the absorbance of the two beamsplittersis zero, then the optimum reflectance value R1 equals 0.50 and theoptimum reflectance value R2 equals 0.50. Alternatively, if it isdesired to achieve a light level ratio between sensor 116 and sensor 128of 10:1, and a light level ratio between sensor 116 and sensor 134 of100:1, and the absorbance of the two beamsplitters is zero, then theoptimum reflectance value R1 equals 0.10 and the optimum reflectancevalue R2 equals 0.10. Or, if it is desired to achieve a light levelratio between sensor 116 and sensor 128 of 3:1, and a light level ratiobetween sensor 116 and sensor 134 of 5:1, and the absorbance of the twobeamsplitters is zero, then the optimum reflectance value R1 equals 0.40and the optimum reflectance value R2 equals 0.50.

In another example it is useful that the light levels of the images oneach of the sensors are equal. Thus if it is desired to achieve a lightlevel ratio between sensor 116 and sensor 128 of 1:1, and a light levelratio between sensor 116 and sensor 134 of 1:1, and the absorbance ofthe two beamsplitters is zero, then the optimum reflectance value R1equals 0.90 and the optimum reflectance value R2 equals 0.90. In thiscase, each of the three sensors 116, 128, and 134 capture substantiallyidentical images with substantially identical light levels.

When all three sensors are caused to capture substantially identicalimages with substantially identical light levels, the moment of imagecapture for each of the three individual sensors 116, 128, and 134 mayoptionally be precisely staggered in such a way that the individualmovie frames successively captured by each of the three sensors may beinterleaved, thereby providing a moving image film with triple theframerate of any one sensor. The invention may be extended to largernumbers of sensors, and in such a way may be used to increase theframerate by a factor of 4, 5, 6, or more times the framerate of oneindividual sensor, thereby enabling a camera having a normal framerateto be used as a super high-speed camera. This high speed cameraapplication is applicable to all of the embodiments of the presentinvention described herein.

FIG. 1B is a schematic diagram of embodiment 1300 of the presentinvention. Referring to FIG. 1B, optical radiation 160 preferably froman object (not shown) is incident on imaging lens system 162.Image-forming beam 164 exits the imaging lens system 162 as a convergingimage beam and is incident on beamsplitter 168, preferably oriented at a45-degree angle to the path of image-forming beam 164. Beamsplitter 168is preferably thin; for example it may be 0.5 mm thick and compriseglass with flat and parallel front and back surfaces; or alternativelyit may comprise a so-called “pellicle” beamsplitter, such as Part NumberNT39-482 from Edmund Optics.

As a result of this beamsplitter arrangement, first reflected beamportion 176 is directed toward image sensor 178, where it forms animage, and first transmitted beam portion 172 is incident onbeamsplitter 174, which is preferably oriented perpendicular to firsttransmitted beam portion 172. As a result, second transmitted beamportion 170 forms an image on image sensor 166, while second reflectedbeam portion 180 returns toward beamsplitter 168, which reflects thirdreflected beam portion 182, which forms an image on image sensor 184.

In order to avoid vignetting (obscuration of a portion of light reachinga detector) of image-forming beam 164, the distance D1 between the backof imaging lens system 162 and the center of beamsplitter 168, distanceD2 between the center of beamsplitter 168 and the center of beamsplitter174, and the distance D3 between the center of beamsplitter 168 and thecenter of image sensor 184 are each preferably greater than or equal toone-half of the diameter of image forming beam 164. Unless variations infocus are desired (as discussed below), the total optical path lengthtraveled by the image forming beam 164 is preferably the same whenmeasured over its total path to each of sensors 166, 178, and 184. Inthat case the distance between the center of beamsplitter 168 and thecenter of image sensor 176 is equal to [D3+(2*D2)], and the distancebetween the center of beamsplitter 174 and the center of image sensor166 is equal to [D2+D3]. Furthermore, the back focal distance, which isthe distance between the back of the imaging lens system 112 and itsnatural focal plane, is preferably approximately equal to[D1+(2*D2)+D3]. In this case, the images formed on each of the imagesensors are substantially identical, preferably except for differentlight levels, as described next.

The portion of the radiant power of the original image forming beam 164that is present in the image formed on image sensor 178 is equal to R1,where R1 is the reflectance of beamsplitter 168. The value of R1 may bechosen to be anything in the range between 0 and 1.0. The portion of theradiant power of the original image forming beam 164 that is present inthe image formed on image sensor 128 is equal to [(1−R1−A1)*(1−R2−A2)],where A1 is the absorbance of beamsplitter 168, and R2 is thereflectance and A2 is the absorbance of beamsplitter 174. The value ofR2 may be chosen to be anything in the range between 0 and 1.0. Theportion of the radiant power of the original image forming beam 114 thatis present in the image formed on image sensor 184 is equal to[R1*R2*(1−R1−A1)]. With these three equations, any set of light levelratios between the sensor 116, sensor 128, and sensor 134 may beachieved by selecting the proper values for R1 and R2.

As can be seen, embodiment 1300 is similar to embodiment 100 except thatbeamsplitter 174 splits first transmitted beam portion 172 instead offirst reflected beam portion 176. Embodiment 1400 is a similar variationon embodiment 600. Thus the present invention may be realized by similarvariations in the order or arrangement of the beamsplitters in any ofthe embodiments described herein.

FIG. 2 is a schematic diagram of embodiment 200 of the presentinvention. Referring to FIG. 2, optical radiation 210 preferably from anobject (not shown) is incident on imaging lens system 212. Image-formingbeam 214 exits imaging lens system 212 as a converging image beam and isincident on beamsplitter 218, which is preferably oriented at a45-degree angle to the path of image-forming beam 214. As a result,first transmitted beam portion 220 continues toward image sensor 216,and first reflected beam portion 222 is reflected toward beamsplitter224, which is preferably oriented perpendicular to first reflected beamportion 222. As a result, second transmitted beam portion 226 passesthrough beamsplitter 224 and forms an image on image sensor 228. Secondtransmitted beam portion 226 typically does not need to pass through acorrective lens system since neither it nor light beams 210, 214, or 222ever pass through tilted beamsplitter 218.

First transmitted beam portion 220 passes through first corrective lenssystem 240, and corrected beam 242 forms an image on image sensor 216.Corrective lens system 240 is preferably designed to adapt to theparticularities of imaging lens system 212 in conjunction withbeamsplitter 218 and in conjunction with the particular distancetraveled by the light beams 214 and 220, in order to ensure that a goodquality image is formed on image sensor 216. The exact design ofcorrective lens system 240 typically depends upon the design of theimaging lens system 212 and on the material and thickness ofbeamsplitter 218. The design of corrective lens system 240 is typicallya straightforward matter for those skilled in the art of lens design andimaging lens system correction. Corrective lens system 240 is preferablycoated, on all optical surfaces, with anti-reflective coatings.

Beamsplitter 218 is preferably coated on its first surface 217 with apartially-reflecting broadband coating, and is preferably coated on itssecond surface 219 with an anti-reflective coating. Beamsplitter 224 ispreferably coated on its first surface 223 with a partially-reflectingcoating, and preferably coated on its second surface 225 with ananti-reflective coating.

Second reflected beam portion 230 is transmitted through beamsplitter218. As a result, third transmitted beam portion 232 passes throughsecond corrective lens system 248. Corrected beam 250 then forms animage on image sensor 234. Corrective lens system 248 is preferablydesigned to adapt to the particularities of the imaging lens system 212in conjunction with beamsplitter 218, and in conjunction with theparticular distance traveled by the light beams 214, 222, 230, and 232,in order to ensure that a good quality image is formed on image sensor234. The exact design of corrective lens system 248 may depend upon thedesign of the imaging lens system 212 and on the material and thicknessof beamsplitter 218. The design of corrective lens system 248 istypically a straightforward matter for those skilled in the art of lensdesign and imaging lens system correction. Corrective lens system 248 ispreferably coated, on all optical surfaces, with anti-reflectivecoatings.

Corrective lens systems 240 and 248 are intended to correct theaberrations (including but not limited to astigmatism and/or coma)induced by passage of image forming beam 214 through beamsplitter 218,which typically comprises (or can be thought of as) a tilted flat plateof glass surrounded by air. The presence of corrective lens systems 240and 248 enables beamsplitter 218 to be thicker and therefore morerugged, since pellicles and other thin beamsplitters are typically veryfragile. The design of such corrective lens systems is a straightforwardmatter for those skilled in the art of lens design. For optimalperformance, corrective lens systems 240 and 248 are preferablydifferent from one another in form and function, each being individuallydesigned to correct the beam at its particular location. However, thisis not necessary for the function of this embodiment and it is possibleto have good correction using corrective lens systems 240 and 248 thatare identical in form and/or function. Because corrective lens system240 is preferably designed in such a way that it is complementary toimaging lens system 212 together with the tilted flat glass platerepresented by beamsplitter 218, imaging lens system 212, beamsplitter218 and first corrective lens system 240 collectively form an imagingsystem that produces a good image on image sensor 216. Likewise, imaginglens system 212, beamsplitter 218, and second corrective lens system 248collectively form an imaging system that produces a good image on imagesensor 234. The images formed on the sensors 216, 228, and 234 are allpreferably substantially identical except for different light levels (oralternatively different focuses, as described below).

FIG. 3 is a schematic diagram of embodiment 400 of the presentinvention. Referring to FIG. 3, optical radiation 410 preferably from anobject (not shown) is incident on imaging lens system 412. Image-formingbeam 414 exits imaging lens system 412 and is incident on beamsplitter418, which is preferably oriented at a 45-degree angle to the path ofimage-forming beam 414. As a result, first transmitted beam portion 420continues on its path toward image sensor 416, and first reflected beamportion 422 is reflected toward beamsplitter 424. After passing throughbeamsplitter 418, first transmitted beam portion 420 forms a firstsub-image on image sensor 416. First reflected beam portion 422 next isincident on beamsplitter 424, which is preferably oriented perpendicularto first reflected beam portion 422. As a result, second transmittedbeam portion 426 passes through beamsplitter 424 and forms an image onimage sensor 428, while second reflected beam portion 430 passes throughbeamsplitter 418. As a result, third transmitted beam portion 432 formsan image on image sensor 434.

Beamsplitter 424 preferably comprises a flat glass or plastic windowwith parallel optical faces, or may alternatively comprise a so-called“pellicle” beamsplitter, such as Part Number NT39-482 from EdmundOptics. Beamsplitter 424 is preferably coated on its first surface 423with a partially-reflecting coating, and preferably coated on its secondsurface 425 with an anti-reflective coating. Beamsplitter 418 is alsopreferably coated on its front surface 417 with a partially-reflectingbroadband coating, and coated on its back surface 419 with ananti-reflective coating. In this embodiment 400, beamsplitter 418preferably comprises a flat front surface 417 and a curved back surface419. The exact shape of the curved back surface 419 is preferablydesigned so that it corrects (or at least partially corrects) theaberrations imparted by beamsplitter 418 onto the two transmittedimage-forming beam portions 420 and 432. This enables beamsplitter 418to be thicker, and therefore more rugged, while eliminating the need forcorrective lens systems such as those used in embodiment 200. The designof such corrective lens shapes is a straightforward matter for thoseskilled in the art of lens design.

FIG. 4 is a schematic diagram of embodiment 1100 of the presentinvention. Referring to FIG. 4, optical radiation 460 preferably from anobject (not shown) is incident on imaging lens system 462. Image-formingbeam 464 exits imaging lens system 462 as a converging image beam and isincident on beamsplitter 468, which is preferably oriented at a45-degree angle to the path of image-forming beam 464. After passingthrough beamsplitter 468, first transmitted beam portion 470 forms animage on image sensor 466, and first reflected beam portion 472 isreflected toward and is incident on beamsplitter 474, which ispreferably oriented perpendicular to first reflected beam portion 472.As a result, second transmitted beam portion 476 passes throughbeamsplitter 474, and forms a second image on image sensor 478, whilesecond reflected beam portion 480 passes through beamsplitter 468. As aresult, third transmitted beam portion 482 forms an image on imagesensor 484.

Beamsplitter 474 preferably comprises a flat glass or plastic windowwith parallel optical faces, and is preferably coated on its firstsurface 473 with a partially-reflecting coating, and preferably coatedon its second surface 475 with an anti-reflective coating.Alternatively, beamsplitter 474 may comprise a so-called “pellicle”beamsplitter, such as Part Number NT39-482 from Edmund Optics.Beamsplitter 468 preferably comprises two different glass types bondedtogether in a manner similar to the one in which two different glasstypes are bonded or cemented together to form an achromatic doubletlens. The advantage to be gained by using such a bonded doubletbeamsplitter is that it can be designed in such a way as to help correctchromatic aberrations. The design of such achromatic doublets is astraightforward matter those skilled in the art of lens design. Morethan two different glass types may alternatively be bonded together toform a triplet (or greater number of elements) lens.

Beamsplitter 468 preferably comprises a flat front surface 467 and acurved back surface 469. The exact shape of back surface 469 ispreferably designed so that it corrects (or at least partially corrects)the aberrations imparted by beamsplitter 468 onto the two image-formingtransmitted beam portions 470 and 482. The design of such correctivelens shapes is a straightforward matter for those skilled in the art oflens design. Beamsplitter 468 is preferably coated on its front surface467 with a partially-reflecting broadband coating, and preferably coatedon its back surface 469 with an anti-reflective coating.

Because of similar geometries, the reflectance equations of embodiment100 may be applied to embodiments 200, 400, and 1100 as well.

FIG. 5A illustrates a schematic diagram of embodiment 600 of the presentinvention. Referring to FIG. 5A, optical radiation 610 preferably froman object (not shown) is incident on imaging lens system 612. Anyimaging lens system may be used in this embodiment of the invention. Forexample, any of the camera lenses manufactured by Nikon, Olympus,Panavision, or Thales Angenieux may be used as the imaging lens system612. Image-forming light 614 exits imaging lens system 612 as aconverging image beam and is incident on beamsplitter 618, which ispreferably oriented at a 45-degree angle to the path of image-formingbeam 614. Image-forming beam 614 that is incident on beamsplitter 618 ispartially reflected and partially transmitted. First reflected beamportion 622 forms an image on image sensor 628. First transmitted beamportion 620 is incident on beamsplitter 624, which is preferablyoriented at a 45-degree angle to the path of first transmitted beamportion 620 and at a ninety degree angle to beamsplitter 618. As aresult of this beamsplitter arrangement, second reflected beam portion632 forms a second image on image sensor 634. Second transmitted beamportion 626 forms an image on image sensor 616.

Beamsplitters 618, 624 are preferably thin. For example they may be 0.5mm thick and comprise glass with flat and parallel front and backsurfaces, or alternatively may comprise a so-called “pellicle”beamsplitter, such as Part Number NT39-482 from Edmund Optics. Inpractice, it has been found that, in order to ensure substantiallyidentical images, the thickness of each beamsplitter 618, 624 ispreferably less than approximately 100 times the greater of either ofthese two values: (a) the pixel width of an individual pixel in imagesensor 616; or (b) the diffraction spot size—or Airy disc diameter—ofimaging lens system 612. The reason for this thickness constraint isthat geometric aberrations caused by the tilted glass/air interfaces ofbeamsplitters 618, 624 increase in size as the thickness ofbeamsplitters 618, 624 increases.

In this embodiment 600, in order to avoid vignetting of image-formingbeam 614, the distance D1 between the back of imaging lens system 612and the center of beamsplitter 618 is preferably greater than or equalto one-half of the diameter of image forming beam 614. The distance D2between the center of beamsplitter 618 and the center of beamsplitter624 is preferably greater than or equal to the diameter of the imageforming beam 614. The distance D3 between the center of beamsplitter 624and the center of sensor 616 is preferably greater than or equal toone-half of the diameter of image forming beam 614. For mostapplications, the total optical path length traveled by the imageforming beam 614 is preferably the same when measured over its totalpath to each of the sensors 628, 616, and 634. Thus the distance betweenthe center of beamsplitter 618 and the center of image sensor 628 ispreferably equal to (D3+D2) and the distance between the center ofbeamsplitter 624 and the center of image sensor 634 is preferably equalto D3. Furthermore, the back focal distance, which is the distancebetween the back of the imaging lens system 612 and its natural focalplane, is preferably approximately equal to (D1+D2+D3). In this case,the images formed on each of the image sensors are substantiallyidentical, preferably except for different light levels, as describednext.

Of the radiant power of the original image forming beam 614, the portionthat is present in the image formed on image sensor 628 is equal to R1,where R1 is the reflectance of beamsplitter 618. The value of R1 may bechosen to be anything in the range between 0 and 1.0. Of the radiantpower of the original image forming beam 614, the portion that ispresent in the image formed on image sensor 634 is equal to[R2*(1−R1−A1)], where A1 is the absorbance of beamsplitter 618 and R2 isthe reflectance of beamsplitter 624. The value of R2 may be chosen to beanything in the range between 0 and 1.0. Of the radiant power of theoriginal image forming beam 614, the portion that is present in theimage formed on image sensor 616 is equal to [(1−R2−A2)*(1−R1−A1)],where A2 is the absorbance of beamsplitter 624. With these threeequations, any set of light level ratios between the sensors 628, 634,and 616 may be achieved by selecting the proper values for R1 and R2.

For example, if it is desired to achieve a light level ratio betweensensor 628 and sensor 634 of 2:1, and a light level ratio between sensor628 and sensor 616 of 4:1, and the absorbance of the two beamsplittersis zero, then the optimum reflectance value R1 equals 0.5714 and theoptimum reflectance value R2 equals 0.6667. Alternatively, if it isdesired to achieve a light level ratio between the sensor 628 and sensor634 of 10:1, and a light level ratio between sensor 628 and sensor 616of 100:1, and the absorbance of the two beamsplitters is zero, then theoptimum reflectance value R1 equals 0.901 and the optimum reflectancevalue R2 equals 0.909. Or, if it is desired to achieve a light levelratio between sensor 628 and sensor 634 of 3:1, and a light level ratiobetween sensor 628 and sensor 616 of 5:1, and the absorbance of the twobeamsplitters is zero, then the optimum reflectance value R1 equals0.6522 and the optimum reflectance value R2 equals 0.6249.

In another example, if it is desired to achieve a light level ratiobetween sensor 628 and sensor 634 of 1:1, and a light level ratiobetween sensor 628 and sensor 616 of 1:1, and the absorbance of the twobeamsplitters is zero, then the optimum reflectance value R1 equals0.3333 and the optimum reflectance value R2 equals 0.50. In thisexample, each of the three sensors 628, 634, and 616 capture images withsubstantially identical light levels.

When all three sensors are caused to capture images with substantiallyidentical light levels, in contrast to the constraint of equal opticalpath lengths as described above, the total optical path length traveledby the image forming beam 614 may intentionally be made to be slightlydifferent when measured over its total path to each of the sensors 628,616, and 634, in order to provide an apparatus that captures threesimultaneous images, substantially identical except for differentfocuses. Thus, the same scene is simultaneously captured in multipleimages each having a different focus. In one application, a cameramanwould not need to change focus during filming of a scene or duringpanning; the focus change (i.e. switching from one image having a firstfocus to another image having a second focus) could be made during postprocessing. Although this application may be accomplished with any ofthe embodiments described herein, it is easier to perform with theembodiments having two beamsplitters arranged at ninety degrees to oneanother (i.e. those shown in FIGS. 5, 6, 7, 13, and 17). (However, inFIG. 17, because the light beam is collimated over most of the pathlength, different focus of each sensor is determined not by the totalpath length, but by the distance between each image sensor and thecorresponding imaging lens. Alternatively, each imaging lens may bedesigned appropriately to provide a different focus, even if thedistances between each image sensor and the corresponding imaging lensare the same.)

FIG. 5B illustrates a schematic diagram of embodiment 1400 of thepresent invention. Referring to FIG. 5B, optical radiation 1110preferably from an object (not shown) is incident on imaging lens system1112. Image-forming light 1114 exits imaging lens system 1112 as aconverging image beam and is incident on beamsplitter 1118, which ispreferably oriented at a 45-degree angle to the path of image-formingbeam 1114. Image-forming beam 1114 that is incident on beamsplitter 1118is partially reflected and partially transmitted. First transmitted beamportion 1120 forms an image on image sensor 1116. First reflected beamportion 1122 is incident on beamsplitter 1124, which is preferablyoriented at a 45-degree angle to the path of first reflected beamportion 1122 and at a ninety degree angle to beamsplitter 1118. As aresult of this beamsplitter arrangement, second reflected beam portion1132 forms a second image on image sensor 1134. Second transmitted beamportion 1126 forms an image on image sensor 1128.

Beamsplitters 1118, 1124 are preferably thin. For example they may be0.5 mm thick and comprise glass with flat and parallel front and backsurfaces, or alternatively may comprise a so-called “pellicle”beamsplitter, such as Part Number NT39-482 from Edmund Optics.

In this embodiment 1400, in order to avoid vignetting of image-formingbeam 1114, the distance D1 between the back of imaging lens system 1112and the center of beamsplitter 1118 is preferably greater than or equalto one-half of the diameter of image forming beam 1114. The distance D2between the center of beamsplitter 1118 and the center of beamsplitter1124 is preferably greater than or equal to the diameter of the imageforming beam 1114. The distance D3 between the center of beamsplitter1124 and the center of sensor 1128 is preferably greater than or equalto one-half of the diameter of image forming beam 1114. For mostapplications, the total optical path length traveled by the imageforming beam 1114 is preferably the same when measured over its totalpath to each of the sensors 1128, 1116, and 1134. Thus the distancebetween the center of beamsplitter 1118 and the center of image sensor1116 is preferably equal to (D3+D2) and the distance between the centerof beamsplitter 1124 and the center of image sensor 1134 is preferablyequal to D3. Furthermore, the back focal distance, which is the distancebetween the back of the imaging lens system 1112 and its natural focalplane, is preferably approximately equal to (D1+D2+D3). In this case,the images formed on each of the image sensors are substantiallyidentical, preferably except for different light levels, as describednext.

Of the radiant power of the original image forming beam 1114, theportion that is present in the image formed on image sensor 1116 isequal to (1−R1−A1), where R1 is the reflectance and A1 is the absorbanceof beamsplitter 1118. The value of R1 may be chosen to be anything inthe range between 0 and 1.0. Of the radiant power of the original imageforming beam 1114, the portion that is present in the image formed onimage sensor 1134 is equal to [R2*R1], where R2 is the reflectance ofbeamsplitter 1124. The value of R2 may be chosen to be anything in therange between 0 and 1.0. Of the radiant power of the original imageforming beam 1114, the portion that is present in the image formed onimage sensor 1128 is equal to [(1−R2−A2)*R1], where A2 is the absorbanceof beamsplitter 1124. With these three equations, any set of light levelratios between the sensors 1128, 1134, and 1116 may be achieved byselecting the proper values for R1 and R2.

FIG. 6 is a schematic diagram of embodiment 700 of the presentinvention. Referring to FIG. 6, optical radiation 710 preferably from anobject (not shown) is incident on imaging lens system 712. Image-forminglight 714 exits imaging lens system 712 as a converging image beam andis incident on beamsplitter 718, which is preferably oriented at a45-degree angle to the path of image-forming light beam 714. As aresult, first reflected beam portion 722 is reflected toward and formsan image on image sensor 728. First transmitted beam portion 720 isincident on beamsplitter 724, which is preferably oriented at a45-degree angle to the path of first transmitted beam portion 720 andoriented at a ninety degree angle to beamsplitter 718, and forms secondtransmitted beam portion 726 second reflected beam portion 732.

Beamsplitter 718 is preferably coated on its first surface 717 with apartially-reflecting broadband coating, and preferably coated on itssecond surface 719 with an anti-reflective coating. Similarly,beamsplitter 724 is preferably coated on its first surface 723 with apartially-reflecting coating, and preferably coated on its secondsurface 725 with an anti-reflective coating.

Second transmitted beam portion 726 next passes through corrective lenssystem 740, and corrected beam 742 forms an image on image sensor 716.Corrective lens system 740 is preferably designed to adapt to theparticularities of imaging lens system 712 in conjunction with theparticular distance traveled by the light beam portions 714, 720, and726, in order to ensure that a good quality image is formed on imagesensor 716. The exact design of corrective lens system 740 will dependupon the design of imaging lens system 712 and on the materials andthicknesses of beamsplitters 718 and 724. Specifically, corrective lenssystem 740 is intended to correct the aberrations induced by passage ofthe image forming beam 714 through beamsplitters 718 and 724, which eachmay comprise or may be thought of as a tilted flat plate of glass.Corrective lens system 740 is preferably coated on all optical surfaceswith anti-reflective coatings. The design of corrective lens system 740is a straightforward matter for those skilled in the art of lens designand imaging lens system correction.

Second reflected beam portion 732 passes through corrective lens system748, and corrected beam 750 forms an image on image sensor 734.Corrective lens system 748 is preferably designed to adapt to theparticularities of imaging lens system 712 in conjunction with theparticular distance traveled by light beam portions 714, 722, and 732,in order to ensure that a good quality image is formed on image sensor734. The exact design of corrective lens system 748 will depend upon thedesign of imaging lens system 712 and on the material and thickness ofbeamsplitter 718. Specifically, corrective lens system 748 is intendedto correct the aberrations induced by passage of image forming beam 714through beamsplitter 718. Corrective lens system 748 is preferablycoated, on all optical surfaces, with anti-reflective coatings. Thedesign of corrective lens system 748 is a straightforward matter forthose skilled in the art of lens design and imaging lens systemcorrection.

For optimal performance, corrective lens systems 740 and 748 arepreferably different from one another in form and function, each beingindividually designed to correct the beam at its particular location,although this is not necessary for the invention's function, and it ispossible to have good correction if corrective lens systems 740 and 748are identical in form. Corrective lens system 740 is preferably designedin such a way that it is complementary to imaging lens system 712together with the effective tilted flat glass plates of beamsplitter 718and 724. In this way, imaging lens system 712, beamsplitter 718,beamsplitter 724, and corrective lens system 740 collectively form animaging system that produces a good image on image sensor 716. Likewise,imaging lens system 712, beamsplitter 718, and corrective lens system748 collectively form an imaging system that produces a good image onimage sensor 734. The images formed on sensors 728, 716, and 734 arepreferably substantially identical to one another except for differentlight levels or focuses, as described above.

FIG. 7 is a schematic diagram of embodiment 1200 of the presentinvention. Referring to FIG. 7, optical radiation 660 preferably from anobject (not shown) is incident on imaging lens system 662. Image-forminglight beam 664 exits imaging lens system 662 as a converging image beamand is incident on beamsplitter 668, which is preferably oriented at a45-degree angle to the path of image-forming light beam 664. As aresult, first reflected beam portion 672 is reflected toward, and formsan image on, image sensor 678. First transmitted beam portion 670 isincident on beamsplitter 674, which is preferably oriented at a45-degree angle to the path of first transmitted beam portion 670. As aresult, second transmitted beam portion 676 forms an image on imagesensor 666, and second reflected beam portion 682 is reflected toward,and forms an image on, image sensor 684.

Beamsplitter 668 preferably comprises a flat front surface 667, whichpreferably comprises a partially-reflecting broadband coating, and acurved back surface 669, which preferably comprises an anti-reflectivecoating. The exact shape of the curved back surface 669 is preferablydesigned so that it corrects (or at least partially corrects) theaberrations imparted by beamsplitter 668 on first transmitted beamportion 670. Beamsplitter 674 preferably comprises a curved frontsurface 673, which preferably comprises a partially-reflecting coating,and a curved back surface 675, which preferably comprises ananti-reflective coating. Front surface 673 may optionally be flat. Theexact shapes of curved front surface 673 and curved back surface 675 arepreferably designed so that beamsplitter 674 corrects (or at leastpartially corrects) the aberrations imparted by beamsplitters 668 and674 on second transmitted beam portion 676. The exact designs of curvedfront surface 673 and curved back surface 675 will depend upon thedesign of imaging lens system 662 and on the material and thickness ofbeamsplitter 668 and on the design of curved back surface 669 ofbeamsplitter 668.

Back surface 669 of beamsplitter 668 and front surface 673 and backsurface 675 of beamsplitter 674 are preferably all designed to work inconcert so as to adapt to the particularities of imaging lens system 662in conjunction with the particular distance traveled by the beamportions 664, 670, 676, and 682 in order to ensure that good quality,well-corrected images are simultaneously formed on image sensors 666 and684. These corrective surfaces enable beamsplitters 668 and 674 to bethicker, and therefore more rugged, while eliminating the need forcorrective lens systems such as those used in embodiment 700. The designof such corrective lens shapes is a straightforward matter for thoseskilled in the art of lens design.

For optimal performance, it is preferred that corrective surfaces 669,673, and 675 are all different from one another in form and function,each preferably being individually designed to correct the beam at itsparticular location, although this is not necessary for the invention'sfunction and it is possible to have good correction if surfaces 669,673, and 675 are identical in form. Note also that back surface 669 ispreferably designed in such a way that it is complementary to imaginglens system 662 together with the tilted flat glass plate represented bybeamsplitter 668 and with front surface 673 and back surface 675 ofbeamsplitter 674. In this way, imaging lens system 662, beamsplitter668, and beamsplitter 674 collectively form an imaging system thatproduces a good image on image sensor 666. Likewise, imaging lens system662, beamsplitter 668, and front surface 673 of beamsplitter 674collectively form an imaging system that produces a good image on imagesensor 684. The images formed on sensors 678, 666, and 684 arepreferably all substantially identical to one another.

Similar to embodiment 1100, either or both of beamsplitters 668 and 674may optionally comprise two different glass types bonded together in amanner similar to the one in which two different glass types are bondedor cemented together to form an achromatic doublet lens. The advantageto be gained by using such a bonded doublet beamsplitter is that it canbe designed in such a way as to help correct chromatic aberrations. Thedesign of such achromatic doublets is a straightforward matter thoseskilled in the art of lens design. More than two different glass typesmay alternatively be bonded together to form a triplet (or greaternumber of elements) lens.

Because of similar geometries, the reflectance equations of embodiment600 may be applied to embodiments 700 and 1200 as well.

FIG. 8 is a schematic diagram of an embodiment 300 of the presentinvention. The basic function of this embodiment 300 is identical to thebasic function of embodiment 100, so a detailed description of the lightpaths is not given again. Referring to FIG. 8, optical radiation 310preferably from an object (not shown) is incident on imaging lens system312, which, for the purposes of the dimensions and materials givenherein for this embodiment, preferably comprises acommercially-available large-format film camera lens, such as onemanufactured by Hasselblad having a focal length of 80 mm and anf-number of f/2.8, although any lens system may be used. After passingthrough imaging lens system 312, the light next passes throughcorrective lens system 313, which is preferably designed to adapt to theparticularities of imaging lens system 312 in order to properlypre-correct the light so that it is best suited for traveling through314, 318, and 324. Specifically, because prisms 314, 318, and 324, whichpreferably comprise thick glass, will introduce chromatic and sphericalaberration into image forming beam portions 319, 325, and 327, theprimary function of corrective lens system 313 is to add an equal andopposite amount of aberration, thereby ensuring that image forming beamportions 319, 325, and 327 are all optically well-corrected and thatthey all form high-resolution images. Because the total optical pathlengths for all three beam portions are preferably identical, only onecorrective lens system is required for all three beam portions. Thedesign of the corrective lens system 313 is a straightforward matter forthose skilled in the art of lens design and lens system adaptation.

Corrective lens system 313 preferably comprises an air-spaced doublet,as shown in FIG. 9. Individual lens elements 352 and 354, which comprisecorrective lens system 313, are preferably rotationally symmetric abouttheir central optical axis 350. Lens element 352 preferably comprisesglass with a refractive index at the sodium d-line wavelength (n_(d))equal to 1.7847 and Abbe dispersion value at the sodium d-linewavelength (V_(d)) equal to 25.680, such as N-SF11 manufactured bySchott Glass. Lens element 352 preferably has an edge diameter of 31.0mm and a center thickness (measured along the central optical axis ofrotation 350) of 4.00 mm. Lens element 354 preferably comprises glasswith a refractive index at the sodium d-line wavelength (n_(d)) equal to1.8467 and Abbe dispersion value at the sodium d-line wavelength (V_(d))equal to 23.780, such as N-SF57 manufactured by Schott Glass. Lenselement 354 preferably has an edge diameter of 28.0 mm and a centerthickness (measured along the central optical axis of rotation 350) of3.00 mm.

The shapes of the optical surfaces of lens elements 352 and 354 arepreferably even aspheres, and the surface sag of each even aspheresurface is given by the following even asphere sag equation:z=cr ²/{1+[1−(1+k)c ² r ²]^(1/2)}+α₄ r ⁴+α₆ r ⁶+α₈ r ⁸+α₁₀ r ¹⁰where c is the curvature (the reciprocal of the radius of curvature,which has units of mm), r is the radial coordinate in mm, k is the conicconstant, and α₄, α₆, α₈, and α₁₀ are the coefficients on the fourth,sixth, eighth, and tenth power polynomial terms, respectively. The shapeof first surface 356 of lens element 352 is preferably a convex evenasphere with a radius of curvature of 184.504 mm, a conic constant of−286.156, α₄=2.718e-6 mm⁻³, α₆=−6.116e-8 mm⁻⁵, α₈=1.211e-10 mm⁻⁷, andα₁₀=−3.542e-13 mm⁻⁹. The shape of second surface 358 of lens element 352is preferably a convex even asphere with a radius of curvature of−56.021 mm, a conic constant of −3.062, α₄=6.891e-6 mm⁻³, α₆=−9.066e-8mm⁻⁵, α₈=3.541e-10 mm⁻⁷, and α₁₀=−8.330e-13 mm⁻⁹.

The shape of first surface 360 of lens element 354 is preferably aconcave even asphere with a radius of curvature of −43.175 mm, a conicconstant of 5.173, α₄=5.363e-5 mm⁻³, α₆=−2.496e-7 mm⁻⁵, α₈=1.650e-9mm⁻⁷, and α₁₀=−3.862e-12 mm⁻⁹. The shape of second surface 362 of lenselement 352 is preferably a concave even asphere with a radius ofcurvature of 383.586 mm, a conic constant of −5000.0, α₄=3.810e-5 mm⁻³,α₆=−2.671e-7 mm⁻⁵, α₈=1.656e-9 mm⁻⁷, and α₁₀=−4.221e-12 mm⁻⁹.

The center thickness (measured along the central optical axis ofrotation 350) between the back mounting plane of imaging lens system 312and lens element 352 is preferably 15.0 mm. The center thickness(measured along the central optical axis of rotation 350) between lenselement 352 and lens element 354 is preferably 4.088 mm. The centerthickness (measured along the central optical axis of rotation 350)between lens element 354 and the front face 315 of glass prism 314 ispreferably 3.0 mm.

Referring again to FIG. 8, front face 315 of prism 314 preferablycomprises an anti-reflective coating, and a partially-reflecting coating316 is preferably applied to the back face of prism 314.Partially-reflecting coating 316 preferably reflects 13% of all light,irrespective of wavelength or polarization, and preferably transmits 77%of all light, irrespective of wavelength or polarization. Such apartially-reflecting coating is preferably deposited using a hybridmetal-dielectric coating technology, for example Newport Corporation'scatalog part number MB.1, which offers constant transmittance over allvisible wavelengths and all polarization states.

Prism 318 is preferably placed in contact with, and is preferablycemented to, partially-reflecting coating 316 on the back face of prism314. Alternatively, partially-reflecting coating 316 may be applied tothe front surface of prism 316, and then the coating and prism iscemented to the back face of prism 314. An anti-reflective coating ispreferably applied to back face 317 of prism 318. Image-forming beamportion 319 is transmitted through prism 314, partially-reflectingcoating 316, and prism 318 and forms an image on image sensor 320, whichpreferably comprises a high-definition motion picture CMOS or CCDsensor, such as model SI-1920HD manufactured by Silicon Imaging.

Partially-reflecting coating 322 is applied on either the side face ofthe prism 314 or the front face of prism 324, and the two prisms arethen preferably cemented together. Partially-reflecting coating 322preferably reflects 84% of all light, irrespective of wavelength orpolarization, and preferably transmits 6% of all light, irrespective ofwavelength or polarization. Such a partially-reflecting coating ispreferably deposited using a hybrid metal-dielectric coating technology,for example Newport Corporation's catalog part number MB.1, which offersconstant transmittance over all visible wavelengths and all polarizationstates. An anti-reflective coating is preferably applied to output face323 of glass prism 324. Image-forming beam portion 325 is transmittedthrough prism 314, reflects off partially-reflecting coating 316, and istransmitted again through prism 314, partially-reflecting coating 322,and prism 324 and forms an image on image sensor 326, which preferablycomprises a high-definition motion picture CMOS or CCD sensor, such asmodel SI-1920HD manufactured by Silicon Imaging.

Image sensor 328 is placed at side face 329 of glass prism 318. Ananti-reflective coating is preferably applied to side face 329.Image-forming beam portion 327 forms an image on image sensor 328, whichpreferably comprises a high-definition motion picture CMOS or CCDsensor, such as model SI-1920HD manufactured by Silicon Imaging.

Because partially-reflecting coatings 316 and 322 preferably compriserelatively thin beamsplitters, and the prisms are preferably cementedtogether (thus leaving no air gaps), no aberrations are introduced bytilted coating 316.

FIG. 10A shows a tilted view of prism 314, which is preferably arectangular volume and is preferably made of a low-dispersion glass suchas N-FK51A manufactured by Schott Glass (n_(d)=1.4866, V_(d)=84.468).Prism 314 preferably has a length (denoted by “L₁”) equal to 25.4 mm, awidth (denoted by “W₁”) equal to 25.4 mm, a height (denoted by “H₁”)equal to 25.4 mm, and a back-face angle (denoted by “θ”) equal to 45degrees.

FIG. 10B shows a tilted view of prism 318, which is preferably arectangular volume and is preferably made of a low-dispersion glass suchas N-FK51A manufactured by Schott Glass (n_(d)=1.4866, V_(d)=84.468).Prism 318 preferably has a length (denoted by “L₁+L₂”) equal to 50.8 mm,a width (denoted by “W₂”) equal to 25.4 mm, a height (denoted by “H₂”)equal to 25.4 mm, and a front-face angle (denoted by “θ₂”) equal to 45degrees.

FIG. 100 shows a tilted view of prism 324, which is preferably arectangular volume and is preferably made of a low-dispersion glass suchas N-FK51A manufactured by Schott Glass (n_(d)=1.4866, V_(d)=84.468).Prism 324 preferably has a length (denoted by “L₃”) that is equal to25.4 mm, a width (denoted by “W₃”) equal to 25.4 mm, and a height(denoted by “H₃”) that is equal to 25.4 mm.

As mentioned above, the dimensions, materials, and other characteristicsdescribed in this embodiment are specific to a large-format film cameralens manufactured by Hasselblad having a focal length of 80 mm and anf-number of f/2.8. For other imaging lens systems, different dimensions,materials, and characteristics would be applicable. Because of similargeometries, the reflectance equations of embodiment 100 may be appliedto this embodiment 300 as well.

FIG. 11A is a schematic diagram of a side view of embodiment 500 of thepresent invention as displayed in the y-z plane, where the z-directionis defined as the direction in which the original optical radiation 510is traveling. The y-direction is defined as being perpendicular to thez-direction and points upward in the figure. The x-direction is definedas being perpendicular to both the y- and z-directions, and thereforepoints into the plane of the figure. FIG. 11B is a schematic diagram ofa top view of embodiment 500 of the present invention as displayed inthe x-z plane, in which the x-direction is defined as beingperpendicular to the z-direction and points upward in the figure. They-direction is defined as being perpendicular to both the x- andz-directions, and therefore points out of the plane of the figure. FIG.11C is a schematic diagram of an end view embodiment 500 of the presentinvention, also as displayed in the x-y plane. FIG. 12 is a see throughschematic diagram of a tilted view of embodiment 500 of the presentinvention. The basic function and layout of embodiment 500 is similar tothe basic functional layout of embodiment 300, with the addition of twoextra beamsplitters and the resulting formation of two extra images;therefore, a detailed description of the light paths is not given again.

Referring to FIGS. 11A-C and 12, optical radiation 510 preferably froman object (not shown) is incident on an imaging lens system 512. For thepurposes of the dimensions, materials, and other characteristics citedin the description of this embodiment, imaging lens system 512 ispreferably a commercially-available large-format film camera lens,manufactured by Hasselblad, and having a focal length of 80 mm and anf-number of f/2.8. However, different dimensions, materials, andcharacteristics may be used with a different imaging lens system. Afterpassing through imaging lens system 512, the light next passes throughcorrective lens system 513. Corrective lens system 513 is identical inform and function to corrective lens system 313 in embodiment 300.Beamsplitting cube 514 is placed at the distal end of corrective lenssystem 513. Beamsplitting cube 514 and the other beamsplitting cubes ofthis embodiment are preferably similar in form and function tocommercially-available broadband non-polarizing beamsplitting cubes,such as model number 10BC17 MB.1 manufactured by the NewportCorporation, preferably measures 25.4 mm on each side, and preferablycomprises an anti-reflective coating applied to both its front face 515and its bottom face 529. Beamsplitting cube 514 preferably comprisesinterior partially-reflecting beamsplitter coating 516, which preferablyis achieved using a standard hybrid metal-dielectric reflecting coatingtechnology. The reflectivity of beamsplitter coating 516 is preferably1.0%, and the transmittance of beamsplitter coating 516 is preferably89.0%. It is typical for hybrid-metal-dielectric coatings to absorbabout 10% of all incident radiation.

Beamsplitting cube 518 is preferably cemented as shown to the back faceof beamsplitting cube 514, preferably measures 25.4 mm on each side, andpreferably comprises an anti-reflective coating applied to both its backface 517 and its side face 534. Beamsplitting cube 518 preferablycomprises interior partially-reflecting beamsplitter coating 521, whichpreferably has a reflectivity of 10.0% and a transmittance of 80.0%.Beamsplitting cube 524 is preferably cemented as shown to the top faceof beamsplitting cube 514, preferably measures 25.4 mm on each side, andpreferably comprises an anti-reflective coating applied to both its topface 523 and its side face 535. Beamsplitting cube 524 preferablycomprises interior partially-reflecting beamsplitter coating 536, whichpreferably has a reflectivity of 1.0% and a transmittance of 89.0%.Prior to assembly and cementing of beamsplitting cubes 514, 518, and524, beamsplitter coating 522 is preferably applied to the top face ofbeamsplitting cube 514 and/or to the bottom face of beamsplitting cube524. Beamsplitter coating 522 preferably has a reflectivity of 10.0% anda transmittance of 80.0%.

Image-forming beam portion 519 exiting back face 517 of beamsplittingcube 518 forms an image on sensor 520. The center thickness between backface 517 and sensor 520 is preferably 5.0 mm. Image-forming beam portion527 exiting bottom face 529 of beamsplitting cube 514 forms an image onsensor 528. The center thickness between bottom face 529 and sensor 528is preferably 5.0 mm. Image-forming beam portion 525 exiting top face523 of beamsplitting cube 524 forms an image on sensor 526. The centerthickness between top face 523 and sensor 526 is preferably 5.0 mm.Image-forming beam portion 531 exiting side face 534 of beamsplittingcube 518 forms an image on sensor 532. The center thickness between sideface 534 and sensor 532 is preferably 5.0 mm. Image-forming beam portion533 exiting side face 535 of beamsplitting cube 524 forms an image onsensor 530. The center thickness between side face 535 and sensor 530 ispreferably 5.0 mm. Thus the four beamsplitting coatings 516, 521, 522,536 of this embodiment are configured to simultaneously produce fiveseparate images. However, the present invention may be extended (orreduced) to form practically any number of sub-images by simply addingor removing a certain number of beamsplitters.

In this embodiment the images formed on the five sensors 520, 528, 526,532, and 530 are substantially identical except for different lightlevels, owing to the fact that the light paths taken from the front face515 of first beamsplitting cube 514 to each of the five sensors allprovide different levels of transmittance. More specifically,image-forming beam portion 519 that forms the image on sensor 520 istransmitted through beamsplitter coatings 516 and 521, and thereforecontains 71.200% of the radiant power at front face 515. Image-formingbeam portion 527 that forms the image on sensor 528 is reflected offcoatings 516 and 522 and then transmitted through coating 516, andtherefore contains 0.089% of the radiant power at front face 515.Image-forming beam portion 525 that forms the image on sensor 526 isreflected off coating 516 and then transmitted through coatings 522 and536, and therefore contains 0.712% of the radiant power at front face515. Image-forming beam portion 531 that forms the image on sensor 532is transmitted through beamsplitter coating 516 and reflected offcoating 521, and therefore contains 8.900% of the radiant power at frontface 515. Image-forming beam portion 533 that forms the image on sensor530 is reflected off beamsplitter coating 516, transmitted throughcoating 522, and then reflected off coating 536, and therefore contains0.008% of the radiant power at front face 515.

In other words, the image formed on sensor 530 has 1/8900^(th) the lightlevel of the image formed on sensor 520. The image formed on sensor 528has 1/800^(th) the light level of the image formed sensor 520. The imageformed on sensor 526 has 1/100^(th) the light level of the image formedon sensor 520. And the image formed on sensor 532 has ⅛^(th) the lightlevel of the image formed on sensor 520. Thus, the images formed on thevarious sensors vary in light level by approximately 3 photographicstops from one sensor to the next, for a total range in light exposurevalues of greater than 12 stops.

The values of reflectivity for beamsplitter coatings 516, 521, 536, and522 may alternatively be altered to provide any variation of lightlevels for the images formed on the five sensors 520, 528, 526, 532, and530. For example, if the reflectance of coating 516 is 6.0% and thetransmittance of coating 516 is 84.0%, the reflectance of coating 521 is18.0% and the transmittance of coating 521 is 72.0%, the reflectance ofcoating 536 is 5.0% and the transmittance of coating 536 is 85.0%, andthe reflectance of coating 522 is 20.0% and the transmittance of coating522 is 70.0%, then the image formed on sensor 530 will have 1/228^(th)the light level of the image formed on sensor 520. The image formed onthe second sensor 528 will have 1/60^(th) the light level of the imageformed on sensor 520. The image formed on sensor 526 will have 1/17^(th)the light level of the image formed on sensor 520. And the image formedon 532 will have ¼^(th) the light level of the image formed on sensor520. Thus in this example the images formed on the various sensors varyin light level by approximately 2 photographic stops from one sensor tothe next, for a total range in light exposure values of greater than 8stops.

In another example, if the reflectance of coating 516 is 25.0% and thetransmittance of coating 516 is 65.0%, the reflectance of coating 521 is30.0% and the transmittance of coating 521 is 60.0%, the reflectance ofcoating 536 is 30.0% and the transmittance of coating 536 is 60.0%, andthe reflectance of coating 522 is 57.0% and the transmittance of coating522 is 33.0%, then the image formed on sensor 530 will have 1/16^(th)the light level of the image formed on sensor 520. The image formed onthe second sensor 528 will have ¼^(th) the light level of the imageformed on sensor 520. The image formed on sensor 526 will have ⅛^(th)the light level of the image formed on sensor 520. And the image formedon 532 will have ½ the light level of the image formed on sensor 520.Thus in this example the images formed on the various sensors vary inlight level by approximately 1 photographic stop from one sensor to thenext, for a total range in light exposure values of greater than 4stops.

In general, the light level of image forming beam portion 519, whichforms an image on sensor 520, is equal to the radiant power at the frontface 515 of beamsplitting cube 514 multiplied by the transmittance ofcoating 516, multiplied by the transmittance of coating 521. The lightlevel of image forming beam portion 527, which forms an image on sensor528, is equal to the radiant power at front face 515 multiplied by thereflectance of coating 516, multiplied by the reflectance of coating522, multiplied by the transmittance of coating 516. The light level ofimage forming beam portion 525, which forms an image on sensor 526, isequal to the radiant power at front face 515 multiplied by thereflectance of coating 516, multiplied by the transmittance of coating522, multiplied by the transmittance of coating 536. The light level ofimage forming beam portion 531, which forms an image on sensor 532, isequal to the radiant power at front face 515 multiplied by thetransmittance of coating 516, multiplied by the reflectance of coating521. The light level of image forming beam portion 533, which forms animage on sensor 530, is equal to the radiant power at front face 515multiplied by the reflectance of coating 516, multiplied by thetransmittance of coating 522, multiplied by the reflectance of coating536.

FIG. 13 is a schematic diagram of embodiment 800 of the presentinvention. The basic geometry, function and layout of embodiment 800 issimilar to embodiment 600; therefore, a detailed description of thelight paths is not given again, and the reflectance equations ofembodiment 600 may be applied to this embodiment 800 as well. Referringto FIG. 13, optical radiation 810 preferably from an object (not shown)is incident on an imaging lens system 812. For the purposes of thedimensions, materials, and other characteristics cited in thedescription of this embodiment, imaging lens system 812 is preferably acommercially-available large-format film camera lens, manufactured byHasselblad, and having a focal length of 80 mm and an f-number of f/2.8.However, different dimensions, materials, and characteristics may beused with a different imaging lens system.

After passing through imaging lens system 812, the light next passesthrough corrective lens system 813, which is preferably designed toadapt to the particularities of the imaging lens system 812 in order toproperly pre-correct the light emerging from the imaging lens system sothat it is best suited for traveling through prisms 814, 818, and 824,which preferably comprise thick glass. Specifically, because thick glassprisms will introduce chromatic and spherical aberration into the imageforming beam portions 819, 825, and 827, the primary function ofcorrective lens system 813 is to add an equal and opposite amount ofaberration, thereby ensuring that the image forming beam portions 819,825, and 827 are all optically well-corrected and form high-resolutionimages. The design of the corrective lens system 813 is astraightforward matter for those skilled in the art of lens design andlens system adaptation. Corrective lens system 813 preferably comprisesan air-spaced doublet, as shown in FIG. 14. The two individualcorrective lens elements 852 and 854 which comprise corrective lenssystem 813 are preferably rotationally symmetric about their centraloptical axis 850. Lens elements 852, 854, their surfaces 856, 858, 860,862, and the associated center thicknesses are identical to those incorrective lens system 313 described above.

Referring again to FIG. 13, prism 814 is located near the output end ofimaging lens system 812 and corrective lens system 813 and preferablycomprises an anti-reflective coating on its front face 815.Partially-reflecting beamsplitting coating 816 is applied to the angledback face prism 814. Coating 816 preferably reflects 81% of all light,irrespective of wavelength or polarization, and preferably transmits 9%of all light, irrespective of wavelength or polarization, and ispreferably achieved using a standard hybrid metal-dielectric reflectingcoating technology. Prism 818 is placed in contact with, and ispreferably cemented to, coating 816, which is applied to the back of thefirst glass prism 814. Alternatively, coating 816 may instead oradditionally be applied to the front face of prism 818. Prisms 814 and818 are thus glued together or otherwise attached at beamsplittercoating 816. Similarly, partially-reflecting beamsplitter coating 822 isapplied on one or both of the back face of prism 818 and the front faceof prism 824. Coating 822 preferably reflects 81% of all light,irrespective of wavelength or polarization, and preferably transmits 9%of all light, irrespective of wavelength or polarization. Prisms 818 and824 are preferably cemented, glued, or otherwise attached together sothat coating 822 is located between them.

Image sensor 826 is located near the back face 823 of prism 814.Image-forming beam portion 825 forms an image on image sensor 826. Ananti-reflective coating is preferably applied to the back face 823 ofprism 814. Image sensor 820 is located near the output face 817 of prism824. Image-forming beam portion 819 forms an image on image sensor 820.An anti-reflective coating is preferably applied to the output face 817of prism 824. Image sensor 828 is located near the side face 829 ofprism 818. Image-forming beam portion 827 forms an image on image sensor828. An anti-reflective coating is preferably applied to the side face829 of prism 818. Each image sensor preferably comprises ahigh-definition motion picture CMOS or CCD sensor, such as modelSI-1920HD manufactured by Silicon Imaging.

FIG. 15A shows a tilted view of prism 814, which is preferably arectangular volume, preferably comprises a low-dispersion glass such asN-FK51A manufactured by Schott Glass (n_(d)=1.4866, V_(d)=84.468), andpreferably has a length (denoted by “L₁”) that is equal to 25.4 mm, awidth (denoted by “W₁”) that is equal to 25.4 mm, a height (denoted by“H₁”) that is equal to 50.8 mm, and a back-face angle (denoted by “θ”)that is equal to 45 degrees. The anti-reflection coating on the frontface 815 of prism 814 preferably has a height (denoted by “H₂”) of 25.4mm.

FIG. 15B shows a tilted view of prism 818, which is preferably arectangular volume, preferably comprises a low-dispersion glass such asN-FK51A manufactured by Schott Glass (n_(d)=1.4866, V_(d)=84.468), andpreferably has a length (denoted by “L₁+L₃”) that is equal to 50.8 mm, awidth (denoted by “W₂”) that is equal to 25.4 mm, a front-face angle(denoted by “θ₂”) that is equal to 45 degrees, and a back-face angle(denoted by “θ₃”) that is equal to 45 degrees.

FIG. 15C shows a tilted view of prism 824, which is preferably arectangular volume, preferably comprises a low-dispersion glass such asN-FK51A manufactured by Schott Glass (n_(d)=1.4866, V_(d)=84.468), andpreferably has a length (denoted by “L₃”) that is equal to 25.4 mm, awidth (denoted by “W₃”) that is equal to 25.4 mm, a height (denoted by“H₃”) that is equal to 25.4 mm, and a front-face angle (denoted by “θ₄”)that is equal to 45 degrees.

The present invention may be applied to effectively collimated imagebeams in contrast to the converging image beams (i.e. image-formingbeams) of the previous embodiments. FIG. 16 is a schematic diagram ofembodiment 900 of the present invention. Referring to FIG. 16, opticalradiation 910 preferably from an object (not shown) is incident onimaging lens system 912, which may comprise, for example, a camera lens.The design of imaging lens system 912 is a straightforward matter forthose skilled in the art of lens design. Imaging lens system 912 ispreferably coated on all transmissive optical surfaces withanti-reflective coatings. Image-forming light 902 exits imaging lenssystem 912 and forms an image at intermediate image plane 904. A fieldlens 906 may optionally be placed substantially coincident withintermediate image plane 904 in order to minimize ‘vignetting’, whichcan occur when imaging lens system 912 is non-telecentric. The decisionabout the necessity for, and the design of, field lens 906 arestraightforward matters for those skilled in the art of lens design.Field lens 906 is preferably coated on all transmissive optical surfaceswith anti-reflective coatings.

Diverging light 908 exits the intermediate image plane 904 (and optionalfield lens 906) and is next incident on collimating lens system 911,which is preferably designed, located and oriented in such a way as toeffectively collimate image beam 914. Collimating lens system 911 limitsthe divergence of diverging light 908; otherwise the divergence might beso high that some of the light misses beamsplitter 918. This may occur,for example, if it is desired to set imaging lens system 912 to a lowerf-number, such as an f-stop of one (f/1). The design of the collimatinglens system 911, which may comprise a shaping optic, is astraightforward matter for those skilled in the art of lens design. Thecollimating lens system 911 is preferably coated on all transmissiveoptical surfaces with anti-reflective coatings. Effectively collimatedimage beam 914 is incident on beamsplitter 918, which is preferablyoriented at a 45-degree angle to the path of the effectively collimatedimage beam 914. Beamsplitter 918 is preferably coated on its firstsurface 917 with a partially-reflecting broadband coating, andpreferably coated on its second surface 919 with an anti-reflectivecoating. Alternatively, beamsplitter 918 may comprise a so-called“pellicle” beamsplitter, such as Part Number NT39-482 from EdmundOptics.

First transmitted beam portion 920 next passes through imaging lenssystem 940, which focuses first transmitted beam portion 920 intoimage-forming beam portion 942, which forms an image on image sensor916. Imaging lens system 940 is preferably designed to adapt to theparticularities of imaging lens system 912 in conjunction with optionalfield lens 906, collimating lens system 911, beamsplitter 918, and theparticular distance traveled by the light beams 902, 908, 914, 920, and942, in order to ensure that a good quality image is formed on the firstimage sensor 916. The exact design of imaging lens system 940 willdepend upon the exact designs of imaging lens system 912, optional fieldlens 906, and collimating lens system 911, and on the material andthickness beamsplitter 918. Imaging lens system 940 is preferably coatedon all transmissive optical surfaces with anti-reflective coatings.Imaging lens system 940 may optionally be designed to correctaberrations induced by the passage of the light beam through the tiltedair/glass interfaces of beamsplitter 918 (which may comprise a tiltedflat glass plate), although these aberrations are typically smallbecause the image beam in that region has been effectively collimated bycollimating lens 911 and optional field lens 906. The design of imaginglens system 940 is a straightforward matter for those skilled in the artof lens design.

First reflected beam portion 922 next is incident on beamsplitter 924,which is preferably oriented perpendicular to first reflected beamportion 922. Beamsplitter 924 is preferably coated on its first surface923 with a partially-reflecting coating, and preferably coated on itssecond surface 925 with an anti-reflective coating. Alternatively,beamsplitter 924 may comprise a so-called “pellicle” beamsplitter, suchas Part Number NT39-482 from Edmund Optics. Second transmitted beamportion 926 next passes through imaging lens system 944, which focusesimage-forming beam portion 946 that exits the imaging lens system 944and forms an image on image sensor 928. Imaging lens system 944 ispreferably designed to adapt to the particularities of imaging lenssystem 912 in conjunction with the optional field lens 906, collimatinglens system 911, beamsplitter 925, and the particular distance traveledby light beams 902, 908, 914, 922, 926, and 946, in order to ensure thata good quality image is formed on image sensor 928. The exact design ofimaging lens system 944 will depend upon the exact designs of imaginglens system 912, optional field lens 906, and the collimating lenssystem 911, and on the material and thickness of beamsplitter 925.Imaging lens system 944 is preferably coated on all transmissive opticalsurfaces with anti-reflective coatings. The design of imaging lenssystem 944 is a straightforward matter for those skilled in the art oflens design.

Second reflected beam portion 930 is incident on beamsplitter 918. As aresult, third transmitted beam portion 932 is created and passes throughimaging lens system 948, which focuses it into image-forming beamportion 950, which forms an image on image sensor 934. Imaging lenssystem 948 is preferably designed to adapt to the particularities ofimaging lens system 912 in conjunction with optional field lens 906,collimating lens system 911, beamsplitter 918, and the particulardistance traveled by the light beams 902, 908, 914, 922, 930, 932, and950, in order to ensure that a good quality image is formed on imagesensor 934. The exact design of imaging lens system 948 will depend uponthe exact designs of imaging lens system 912, optional field lens 906,and collimating lens system 911, and on the material and thickness ofbeamsplitter 918. Imaging lens system 948 is preferably coated on alltransmissive optical surfaces with anti-reflective coatings. Imaginglens system 948 may optionally be designed to correct aberrationsinduced by the passage of the light beam through the tilted air/glassinterfaces of beamsplitter 918 (which may comprise a tilted flat glassplate), although these aberrations are typically small because the imagebeam in that region has been effectively collimated by collimating lens911 and optional field lens 906. The design of imaging lens system 948is a straightforward matter for those skilled in the art of lens design.

For optimal performance, it is preferred that imaging lens systems 940,944 and 948 are all different from one another in form and function,each being individually designed to correct the beam at its particularlocation, although this is not necessary for the invention's functionand it is possible to have good function using imaging lens systems thatare identical in form and/or function.

Imaging lens system 940 is preferably designed in such a way that it iscomplementary to imaging lens system 912 together with optional fieldlens 906, collimating lens system 911, and beamsplitter 918. In thisway, imaging lens system 912, optional field lens 906, collimating lenssystem 911, beamsplitter 918, and imaging lens system 940 collectivelyform an imaging system that produces a good image on image sensor 916.Likewise, imaging lens system 912, optional field lens 906, collimatinglens system 911, beamsplitter 925, and imaging lens system 944collectively form an imaging system that produces a good image on imagesensor 928. Similarly, imaging lens system 912, optional field lens 906,collimating lens system 911, beamsplitter 918, and imaging lens system948 collectively form an imaging system that produces a good image onimage sensor 934. The images formed on sensors 916, 928, and 934 arepreferably all substantially identical to one another, typically exceptfor different light levels or focuses.

The use of an effectively collimated image beam has advantages (lessaberrations, lower f-number imaging lens) described above. However, theuse of an effectively collimated image beam makes it necessary toinclude imaging lenses 940, 944 and 948, and thus added complexity, tothe system, compared to the case when the collimating lens 911 is notpresent. In this embodiment, after collimating lens 911 the image beamis effectively collimated until it reaches imaging lenses 944, 940, 948.

Although the images formed on sensors 916, 928, 934 are preferably allsubstantially identical to one another in the present embodiment(optionally except for different light levels or focuses), imaging lenssystems 940, 944, 948 may optionally have different magnifying powers,thus providing an overall imaging system that provides multipledifferent zoom levels and multiple different fields-of-view all througha single imaging lens system 912.

Because of similar geometries, the reflectance equations of embodiment100 may be applied to this embodiment 900 as well.

FIG. 17 is a schematic diagram of embodiment 1000 of the presentinvention. Referring to FIG. 17, optical radiation 1010 preferably froman object (not shown) is incident on imaging lens system 1012, which ispreferably coated on all transmissive optical surfaces withanti-reflective coatings. The design of imaging lens system 1012 is astraightforward matter for those skilled in the art of lens design.Image-forming light beam 1002 exits imaging lens system 1012 and formsan image at intermediate image plane 1004. Field lens 1006 mayoptionally be placed substantially coincident with intermediate imageplane 1004. Field lens 1006 is not strictly necessary in all cases;however, a field lens is often used to help minimize ‘vignetting’.Optional field lens 1006 is preferably coated on all transmissiveoptical surfaces with anti-reflective coatings. The decision about thenecessity for, and the design of, field lens 1006 are straightforwardmatters for those skilled in the art of lens design.

Diverging light 1008 exits intermediate image plane 1004 (and optionalfield lens 1006) and is next incident on collimating lens system 1011,which is preferably located and oriented in such a way that the lightbeam 1014 exiting the collimating lens system 1011 is an effectivelycollimated image beam. Collimating lens system 1011 is preferablycoated, on all transmissive optical surfaces, with anti-reflectivecoatings. The advantages and disadvantages of using a collimated lightbeam are described above in the previous embodiment. The design ofcollimating lens system 1011 is a straightforward matter for thoseskilled in the art of lens design.

Effectively collimated image beam 1014 is incident on beamsplitter 1018,which is preferably oriented at a 45-degree angle to the path of thelight beam 1014. Beamsplitter 1018 is preferably coated on its firstsurface 1017 with a partially-reflecting broadband coating, andpreferably coated on its second surface 1019 with an anti-reflectivecoating. Alternatively, beamsplitter 1018 may comprise a so-called“pellicle” beamsplitter, such as Part Number NT39-482 from EdmundOptics.

First reflected beam portion 1022 next passes through imaging lenssystem 1044, which is preferably designed to adapt to theparticularities of imaging lens system 1012 in conjunction with optionalfield lens 1006, collimating lens system 1011, and the particulardistance traveled by the light beams 1002, 1008, 1014, 1022, and 1046,in order to ensure that a good quality image is formed on image sensor1028. The exact design of the imaging lens system 1044 will depend uponthe exact designs of imaging lens system 1012, optional field lens 1006,and collimating lens system 1011. The imaging lens system 1044 ispreferably coated on all transmissive optical surfaces withanti-reflective coatings. The design of the imaging lens system 1044 isa straightforward matter for those skilled in the art of lens design.After passing through and being focused by imaging lens system 1044,first image-forming beam portion 1046 forms an image on image sensor1028.

First transmitted beam portion 1020 is incident on beamsplitter 1024,which is preferably oriented at a 45-degree angle to the path of firsttransmitted beam portion 1020 and oriented at a 90-degree angle tobeamsplitter 1018. Beamsplitter 1024 is preferably coated on its firstsurface 1023 with a partially-reflecting coating, and preferably coatedon its second surface 1025 with an anti-reflective coating.Alternatively, beamsplitter 1024 may comprise a so-called “pellicle”beamsplitter, such as Part Number NT39-482 from Edmund Optics.

Second transmitted beam portion 1026 next passes through imaging lenssystem 1040, which focuses the beam to form second image-forming beamportion 1042, which forms an image on image sensor 1016. Imaging lenssystem 1040 is preferably designed to adapt to the particularities ofimaging lens system 1012 in conjunction with optional field lens 1006,collimating lens system 1011, beamsplitter 1018, beamsplitter 1024, andthe particular distance traveled by the light beams 1002, 1008, 1014,1020, 1026 and 1042, in order to ensure that a good quality image isformed on image sensor 1016. The exact design of imaging lens system1040 will depend upon the exact designs of imaging lens system 1012,optional field lens 1006, and collimating lens system 1011, and willalso depend upon the materials and thicknesses of beamsplitters 1018 and1024. Imaging lens system 1040 is preferably coated on all transmissiveoptical surfaces with anti-reflective coatings. Imaging lens system 1040may optionally be designed to correct aberrations induced by the passageof the light beam through the tilted air/glass interfaces ofbeamsplitters 1018 and 1024 (which each may comprise a tilted flat glassplate), although these aberrations are typically small because the imagebeam in that region has been effectively collimated by collimating lens1011 and optional field lens 1006. The design of the imaging lens system1040 is a straightforward matter for those skilled in the art of lensdesign.

Second reflected beam portion 1032 passes through and is focused byimaging lens system 1048, and third image-forming beam portion 1050forms an image on image sensor 1034. Imaging lens system 1048 ispreferably designed to adapt to the particularities of imaging lenssystem 1012 in conjunction with optional field lens 1006, collimatinglens system 1011, beamsplitter 1018, and with the particular distancetraveled by light beams 1002, 1008, 1014, 1020, 1032 and 1050, in orderto ensure that a good quality image is formed on image sensor 1034. Theexact design of imaging lens system 1048 will depend upon the exactdesigns of imaging lens system 1012, optional field lens 1006, andcollimating lens system 1011, and will also depend upon the material andthickness of beamsplitter 1018. Imaging lens system 1048 is preferablycoated on all optical surfaces with anti-reflective coatings. Imaginglens system 1048 may optionally be designed to correct aberrationsinduced by the passage of the light beam through the tilted air/glassinterfaces of beamsplitters 1018 and 1024 (which each may comprise atilted flat glass plate), although these aberrations are typically smallbecause the image beam in that region has been effectively collimated bycollimating lens 1011 and optional field lens 1006. The design ofimaging lens system 1048 is a straightforward matter for those skilledin the art of lens design and imaging lens system correction.

For optimal performance, it is preferred that the imaging lens systems1040, 1044 and 1048 are different from one another in form and function,each being individually designed to correct the beam at its particularlocation, although this is not necessary for the invention's functionand it is possible to have good correction using imaging lens systemsthat are identical in form. Imaging lens system 1040 is preferablydesigned in such a way that it is complementary to imaging lens system1012 together with optional field lens 1006, collimating lens system1011, beamsplitter 1018, and beamsplitter 1024 (either or both of whichmay comprise a tilted flat glass plate). In this way, imaging lenssystem 1012, optional field lens 1006, collimating lens system 1011,beamsplitter 1018, beamsplitter 1024, and imaging lens system 1040collectively form an imaging system that produces a good image on imagesensor 1016. Likewise, imaging lens system 1012, optional field lens1006, collimating lens system 1011, and imaging lens system 1044collectively form an imaging system that produces a good image on imagesensor 1028. Similarly, imaging lens system 1012, optional field lens1006, collimating lens system 1011, beamsplitter 1018, and imaging lenssystem 1048 collectively form an imaging system that produces a goodimage on image sensor 1034. The images formed on sensors 1028, 1016, and1034 are preferably all substantially identical to one another, with theexception of different light levels or focuses, depending on theapplication.

Each of the imaging lens systems 1040, 1044, 1048 may optionally bedesigned to provide different magnification, thereby providing a “zoom”magnification effect when comparing images formed on each of the sensors1016, 1028, 1034.

Because of similar geometries, the reflectance equations of embodiment600 may be applied to this embodiment 1000 as well.

Embodiments 900 and 1000 may alternatively utilize solid prisms, similarrespectively to embodiments 300 and 800 described above.

All of the beamsplitters and beam splitting elements described in all ofthe embodiments herein are preferably whole beam broad spectrumbeamsplitters. Thus, the present invention preferably exhibits noparallax error between the separate images. The present invention alsopreferably exhibits no measurable differences in wavelength compositionbetween the separate images.

Using the present invention it is possible to simultaneously obtainmultiple high-resolution images of a scene, which images may be combinedto form a single HDR image. It is therefore possible to obtainhigh-resolution HDR snapshots of moving subjects, as well ashigh-resolution HDR moving pictures (e.g. cinematographic films, movies,or other video) in which the subject and/or camera is moving.

Although the invention has been described in detail with particularreference to these embodiments, other embodiments can achieve the sameresults. Variations and modifications of the present invention will beobvious to those skilled in the art and it is intended to cover in theappended claims all such modifications and equivalents. The entiredisclosures of all references, applications, patents, and publicationscited above are hereby incorporated by reference.

What is claimed is:
 1. A method of creating multiple images, the methodcomprising the steps of: splitting an image-forming optical beam into afirst reflected beam portion and a first transmitted beam portion usinga first non-polarizing whole beam beamsplitter; subsequently splittingthe first reflected beam portion or the first transmitted beam portioninto a second reflected beam portion and a second transmitted beamportion using a second non-polarizing whole beam beamsplitter; the firstbeamsplitter subsequently splitting the second reflected beam portioninto a third reflected beam portion and a third transmitted beamportion; and forming a plurality of images on separate optical detectorsfrom at least some of the beam portions; wherein each beamsplitterproduces a reflected beam portion and a transmitted beam portion whichare substantially identical.
 2. The method of claim 1 wherein the formedimages are substantially identical, substantially identical except fortheir focuses, or substantially identical except for theirmagnifications.
 3. The method of claim 2 wherein the forming stepcomprises simultaneously capturing an image on each optical detector. 4.The method of claim 3 further comprising the steps of: selecting a firstimage formed on a first optical detector from a first set ofsimultaneously captured images; subsequently selecting a second imageformed on a second optical detector from the first set of simultaneouslycaptured images or a second set of simultaneously captured images, thesecond image having a different focus or magnification than the firstimage; and assembling the selected formed images to create a film orvideo.
 5. The method of claim 1 further comprising the step of causingonly one of the optical detectors to capture an image at a time, therebyincreasing a camera framerate.
 6. An apparatus for creating multipleimages, the apparatus comprising: a first non-polarizing whole beambeamsplitter oriented at a forty-five degree angle to an optical axis ofan image forming beam, said first beamsplitter forming a first reflectedbeam portion and a first transmitted beam portion; a secondnon-polarizing whole beam beamsplitter for subsequently splitting thefirst reflected beam portion or the first transmitted beam portion intoa second reflected beam portion and a second transmitted beam portion,said second beamsplitter is oriented at a forty-five degree angle tosaid first beamsplitter; and a plurality of separate optical detectorsfor imaging at least some of the plurality of beam portions; whereineach said beamsplitter produces a reflected beam portion and atransmitted beam portion which are substantially identical.
 7. Theapparatus of claim 6 wherein images formed on said plurality of opticaldetectors are substantially identical, substantially identical exceptfor their focuses, or substantially identical except for theirmagnifications.
 8. The apparatus of claim 7 wherein said plurality ofoptical detectors are configured to simultaneously capture an image oneach optical detector.
 9. The apparatus of claim 7 wherein saidplurality of optical detectors are configured so that only one capturesan image at a time, thereby increasing a camera framerate.